The invention relates to a method to form texture at a surface of a photovoltaic cell.
Light enters a photovoltaic cell and generates current. If any light passes entirely through the cell and escapes without being absorbed, cell efficiency is reduced. Thus methods are employed to increase travel distance of light within a photovoltaic cell, including reducing reflection at the front surface of the cell, reflecting light from the back surface of the cell, and bending light at either the front or back surface. One method to increase travel length of light in a photovoltaic cell is to create texture at the front and/or back surface.
In conventional monocrystalline silicon photovoltaic cells, it is well-known to texture surfaces using a crystallographic etch. One commonly used etch produces pyramids, with maximum peak-to-valley distances on the order of ten microns. Such surface texturing is effective for a wafer which is, for example, 150 microns thick or more. In a photovoltaic cell comprising a significantly thinner silicon lamina, however, this style of texturing may not be practical.
There is a need, therefore, for a method of surface texturing appropriate to a photovoltaic cell comprising a thinner semiconductor lamina.